The present invention relates to a method and apparatus for creating randomly variegated yarn by twisting two or more yarns together, thereby preventing the development of patterning when the resulting yarn is used in textile products.
In the textile industry, two or more yarns are frequently twisted together into a single multi-ply yarn which has desirable characteristics such as improved strength, appearance, texture, wear resistance, ease of handling during manufacturing, or other properties. The yarn plies which are combined may be made up of different fibers, either natural or synthetic, or the yarns may be made up of the same type fiber but have slightly different qualities, even when unintended. The different yarn plies often have varying dye characteristics, and if package dyeing of the combined yarn or piece dyeing is later employed, the yarn plies may attain visibly different color shades, giving the resulting product a variegated appearance. A variegated appearance may also arise from the differing texture or other properties of the individual yarn plies.
While a variegated appearance may be desirable in itself, yarn patterning tends to arise when yarn plies are combined, producing streaks or other patterns which repeat throughout the textile product in which the combined yarn is used. Yarn patterning is caused by the tendency of the yarn plies to interact with mechanical parts, such as feed rollers and traversing drums, in a uniform repeating pattern, which has been difficult to avoid.
U.S. Pat. 4,934,134 to Niederer describes one approach to controlling yarn patterning in which a vortex is employed to randomly twist strands together with varying air pressure controlled by an air controller and a beater interposed in the path of the yarn to randomize the yarn strands. This approach requires an air controller and a mechanical beater which likely results in some ultimate repeating pattern. Further, the Niederer patent does not suggest varying the rate of take-up of the yarn as a means for varying the twist in the plied yarn.
In accordance with the present invention, a method and apparatus for creating randomly variegated pneumatically twisted yarn is provided, in which the problem of yarn patterning is eliminated in a simple and efficient manner.